Methods of neuroprotection involving macrophage colony stimulating factor receptor agonists

ABSTRACT

Disclosed are novel methods for preventing or attenuating neuronal damage or stimulating neuronal repair, prior to or following central nervous system injury associated with acute or chronic nervous system injury. Macrophage colony stimulating factor receptor agonists including macrophage colony stimulating factor (M-CSF or CSF-1), interleukin-34 (IL-34), proteins or biologically active fragments thereof, peptides or biologically active fragments thereof, peptidomimetics, or small molecules, and the like are effective for prevention or treatment of acute nervous system injury or chronic nervous system injury involving Alzheimer&#39;s disease, Parkinson&#39;s disease, amyotrophic lateral sclerosis, Huntington&#39;s disease, and the like.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 13/441,879, filed Apr. 7, 2012, now U.S. Pat. No.9,161,968, which application claims priority to U.S. Provisional PatentApplication Ser. No. 61/473,328, filed Apr. 8, 2011, the disclosures ofwhich applications are herein incorporated by reference.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under AG23708 awarded bythe National Institutes of Health. The government has certain rights inthe invention.

INCORPORATION OF SEQUENCE LISTING

A computer readable form of the sequence listing, “ASB036UTL_ST25.txt”,submitted via EFS-WEB, is herein incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to methods of attenuating neuronal damageand stimulating neuronal repair involving the administration of agentsthat activate the macrophage colony stimulating factor receptor.

BACKGROUND

Traumatic brain injury, cerebral ischemia, metabolic insults such asglucose deprivation and oxidative stress as well as neurodegenerativedisorders can cause permanent neurological damage and are a major causeof mortality and morbidity. Neuronal damage, leading to acutely injuredor degenerating neurons, can also result from aberrant, excessivestimulation of neurons through excitatory neurotransmitters(excitotoxicity), in particular by the excitatory neurotransmitterglutamate.

Neuroprotective factors such as the nerve growth factor, brain-derivedneurotrophic factor, neurotrophin-3, neurotrophin-4, novelneurotrophin-1 or insulin-like growth factor 1 (IGF-1) play an importantrole in the maturation, function, repair and survival of neurons(Sofroniew et al., 2001). Neuronal expression of neuroprotective factorshas been found to be markedly upregulated following seizures, cerebralischemia and other brain injuries, initiating a cascade of events inneurons and surrounding glia cells to prevent further brain damage.

The knowledge about neuroprotective factors has to date not translatedinto effective treatments following neuronal insults and, as a result,current therapies for traumatic brain injury, ischemic stroke andneurodegenerative disorders are inadequate and not sufficient to stopneuronal cell loss and death. It would, therefore, be highly desirableto have therapeutic agents available for immediate treatment followingbrain injuries or even prior to brain injuries to mitigate or to preventneuronal cell death.

SUMMARY OF THE INVENTION

The present invention provides methods for reducing neuronal damage andstimulating neuronal repair following acute or chronic injury of nervecells of the central nervous system. The methods for attenuatingneuronal damage and stimulating neuronal repair following acute orchronic injury of nerve cells of the central nervous system comprise theadministration of macrophage colony stimulating factor receptor agonistslocally at or near a site of injury or systemically in a therapeuticallyeffective amount and within a time period following acute or chronicinjury that is sufficient to provide a therapeutic effect.

Furthermore, the present invention provides methods for preventing orattenuating neuronal damage prior to acute or chronic injury of nervecells of the central nervous system. The methods for preventing orattenuating neuronal damage prior to acute or chronic injury of nervecells of the central nervous system comprise the administration ofmacrophage colony stimulating factor receptor agonists locally orsystemically in a therapeutically effective amount and within a timeperiod prior to acute or chronic injury that is sufficient to provide atherapeutic effect.

In one aspect of the present invention, the macrophage colonystimulating factor receptor agonist is a protein or a biologicallyactive fragment thereof; a peptide or a biologically active fragmentthereof, a peptidomimetic, or a small molecule. In one embodiment of thepresent invention, the macrophage colony stimulating factor receptoragonist is the macrophage colony stimulating factor, M-CSF or CSF-1. Inanother embodiment of the present invention, the macrophage colonystimulating factor receptor agonist is Interleukin-34, IL-34.

The above summary is not intended to include all features and aspects ofthe present invention nor does it imply that the invention must includeall features and aspects discussed in this summary.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate embodiments of the invention and,together with the description, serve to explain the invention. Thesedrawings are offered by way of illustration and not by way oflimitation; it is emphasized that the various features of the drawingsmay not be to-scale.

FIG. 1 illustrates the ability of systemically administered macrophagecolony stimulating factor (M-CSF) to improve cognitive function inhAPP-transgenic mice, as further described in Example 1. In panel A,M-CSF plasma levels in Alzheimer's disease patients and age-matchednon-demented controls are compared. Bars are mean±SEM. ***, P<0.001 byStudent t test. In panel B, hAPP mice and their wildtype (WT)littermates (n=9-10 mice per genotype, age 5.5-6.5 months) were injectedwith M-CSF (800 μg/kg) or PBS three times a week. After 10 weeks oftreatment spatial cognitive function in mice was assessed using thewater maze. In panels C-F, hAPP mice and WT littermates(18-20-month-old) were assessed according to water maze deficits inhidden platform tests (panel C) and a probe trial 24 h later (panel D).The mice were randomly divided into M-CSF or PBS groups (n=6-8 mice pergenotype). After a month of treatment, mice were tested again with watermaze hidden platform test (panel E) and a probe trial (panel F). Thetarget quadrant was quadrant 1 in panel D and panel F. Bars aremean±SEM. **, P<0.01; *, P<0.05 compared by ANOVA and Bonferronipost-hoc test.

FIG. 2 illustrates that M-CSF treatment does not affect cerebral Aβdeposition in hAPP-transgenic mice, as further described in Example 1.HAPP mice and their wildtype (WT) littermates (n=9-10 mice per genotype,5.5-6.5 months of age) were injected M-CSF or PBS (i.p., 800 μg/kg)three times a week for 10 weeks. Mice were sacrificed and one hemibrainwas fixed for immunohistochemistry. Aβ deposition in brain sections wasassessed with antibody 3D6 (Aβ₁₋₅) in hAPP mice. In panel A,representative images from mice treated with M-CSF or PBS as control areshown. Scale bar is 40 μm. Quantification of Aβ deposits, expressed as3D6 immunoreactivity in the cortex (panel B) and the hippocampus (panelC). In panel D, quantification of thioflavin-S staining of hippocampalamyloid plaques is shown, expressed as percentage of hippocampal areacovered by plaques. No significant differences were found between M-CSFor PBS treated groups.

FIG. 3 illustrates that systemic M-CSF attenuates kainic acid-inducedneurodegeneration, as further described in Example 2. Two-month-oldFVB/N mice were lesioned with kainic acid (20 mg/kg, subcutaneousinjection) and sacrificed 5 days later. Recombinant M-CSF (800 μg/kg)was injected intraperitoneally once 24 h before kainic acid. Kainicacid-induced neuronal injury was assessed by cresyl violet staining (A,B), calbindin immunostaining (C, D) and Neuropeptide Y (NPY)immunostaining (E, F), and microglial activation was assessed by CD68immunostaining (G, H). Representative images are shown from hippocampiof mice left untreated (control, left), kainic acid lesioned and treatedwith PBS (middle) or M-CSF (right). Scale bar=200 μm. Bars in (B, D, F,and H) are mean±SEM (n=4-7 mice/group). **, P<0.01; *, P<0.05 comparedby ANOVA and Bonferroni post-hoc test. Similar results were obtainedfrom three independent experiments.

FIG. 4 illustrates that M-CSF does not enhance peripheral cellinfiltration, as further described in Example 3. Actin-GFP mice (donor)were paired with wildtype littermates or hAPP mice (recipient) byparabiosis. In panel A, blood was collected 2 weeks after surgery andcells were analyzed by flow cytometry for GFP expression. Representativeplots showing similar frequencies of GFP+ cells in the transgenic donorand wildtype recipient at the time of blood collection. MFI, meanfluorescence intensity. Panel B shows the number of GFP+ cells in thebrains of recipient parabionts 6 weeks after surgery. In the control andhAPP groups, both parabionts received M-CSF or PBS for 4 weeks. In thekainic acid group, parabionts received one dose of M-CSF or PBS 24 hbefore KA injection and were sacrificed at day 5 after KAadministration. n=3-5 mice per group, 3 sections per mouse.

FIG. 5 illustrates that c-Fms reporter gene is upregulated aftersystemic kainate injury, as further detailed in Example 4. c-Fmsreporter mice (MAFIA mice, 2 month of age) were lesioned with kainicacid (20 mg/kg, subcutaneous injection) and sacrificed 6 and 24 h later.These mice express an EGFP tag under the control of the c-fms promoterso that the expression of c-Fms can be detected by EGFP immunostaining.(A) To test the specificity of the antibody against EGFP, brain sectionsfrom MAFIA mice (left panel), wildtype mice (middle panel) and wildtypemice with kainate injury (right panel) were immunostained. Note EGFPimmunoreactivity is observed only in the EGFP-expressing MAFIA mice, butnot in the wildtypes. (B-E) Representative brain images shown from leftto right were from controls (no injury), kainic acid lesioned andsacrificed at 6 h, and kainic acid lesioned and sacrificed at 24 h.Areas representing the CA1 (C), CA3 (D) and dentate gyrus (E) are shownat higher magnification. Scale bars=200 μm in (A-B), =50 μm in (C-E).

FIG. 6 illustrates that a c-Fms reporter gene is expressed in neuronsand upregulated after excitotoxic brain injury, as further detailed inExample 4. c-Fms reporter mice (MAFIA mice, 2 month of age) werelesioned with kainic acid (20 mg/kg, subcutaneous injection) andsacrificed 6 h later. Brain sections from control (A, C) andkainate-lesioned (B, D) were double immunolabeled with antibodiesagainst EGFP (green) and cell type-specific markers Iba-1 (microglia, A,B) and NeuN (neurons, C, D) (red) and images were taken by a confocalmicroscope. The reporter gene expressing cells appear yellow aftersuperimposition. Note an Iba-1 immuno-negative cell expresses thereporter gene (arrow) in (A). The upregulation of reporter gene inneurons is shown after kainate lesion (D) compared with control (C).Scale bar=20 μm. (E) In situ hybridization with digoxigenin(DIG)-labeled probe for cfins in cultured primary neurons. Thehybridization signal (red) was detected by HNPP Fluorescent DetectionSet.

FIG. 7 illustrates in situ hybridization with digoxigenin (DIG)-labeledprobe for c-fms in cultured primary neurons, as further detailed inExample 4. Primary hippocampal neurons were isolated from 16 days oldCF1 mouse embryos, aged for 6-7 days and hybridized with c-fms probe.Strong hybridization signal was observed in neurons with the anti-senseprobe (right panel), but not the sense probe (left panel).

FIG. 8 illustrates that mature neurons express c-fms-driven reportergene, as further detailed in Example 4. Confocal microscope imageshowing frontal cortex from a c-fms-iCre×ROSA-stop^(flox)-CFP mouseimmunolabeled with an antibody against NeuN (red) and stained with DAPI(blue). Cre recombinase expression driven by the endogenous c-fmspromoter leads to recombination and deletion of the stop codon in frontof Cyan fluorescent protein (CFP). Two bright yellow cells in the imageshow CFP colocalization with NeuN in mature neurons.

FIG. 9 illustrates that the c-Fms reporter gene is upregulated afterstereotaxic kainate injury, as further detailed in Example 4. c-Fmsreporter mice (MAFIA, 2 month of age) were lesioned with a unilateralstereotaxic injection of kainic acid (50 ng, left hemibrain) or PBS(right hemibrain). Mice were sacrificed 6 h later and brain sectionswere analyzed for reporter gene expression by EGFP immunostaining. (A) Arepresentative mouse coronal brain section shows upregulation of thereporter gene in the kainate lesioned side (left hemibrain). (B-D)Rectangles indicate the areas of CA1 (B), CA3 (C) and dentate gyrus (D)shown at higher magnification. Scale bars=400 μm in (A), =50 μm in(B-D).

FIG. 10 illustrates the deletion of the c-Fms receptor inc-fms^(f/f)-cre mutant mice, as further detailed in Example 5. Wildtype(WT) or c-fms^(f/f)-cre littermate mice (2 month of age) were lesionedwith kainic acid (20 mg/kg, subcutaneous injection) and sacrificed 6 hlater. Hippocampi were isolated and subjected to Western blot analysis.(A) Immunoblotting of c-Fms levels in hippocampal homogenates fromwildtype and mutant mice. Actin served as loading control. (B)Quantification of c-Fms levels determined by immunoblotting. **, P<0.01by t test.

FIG. 11 illustrates that deletion of c-Fms in neurons increasessusceptibility to kainic acid-induced excitotoxic injury, as furtherdetailed in Example 5. c-fms^(f/f)-cre mice and their wildtypelittermates (2 month of age) were lesioned with a unilateral stereotaxicinjection of kainic acid (50 ng) or PBS into the hippocampus. Mice weresacrificed 5 days later and brain sections were analyzed for neuronalinjury by cresyl violet staining (A, B), calbindin immunostaining (C, D)and CD68 immunostaining (microglial activation, E, F). In (A, C, E),mice from the wildtype (top panel) and mutant group (bottom panel) areshown. Scale bar=200 μm. Bars in (B, D, F) are mean±SEM (n=3-4mice/group) from one out of two experiments. * P<0.05, ** P<0.01compared with wildtype by student t test.

FIG. 12 illustrates that M-CSF immunoreactivity is absent in op/op mice,as further detailed in Example 6. Wildtype FVB/N mice (2 month of age,top panels) or op/op mice (bottom panels) were lesioned with kainic acid(20 mg/kg, subcutaneous injection) and sacrificed 6 h later. Brainsections were immunostained with an antibody against M-CSF.Representative mice shown from left to right were controls (no injury),kainic acid lesioned and sacrificed at 6 h. Scale bar=200 μm.

FIG. 13 illustrates that endogenous M-CSF is upregulated in neuronsafter excitotoxic brain injury, as further detailed in Example 6.Wildtype FVB/N mice (2 month of age) were lesioned with kainic acid (20mg/kg, subcutaneous injection) and sacrificed 6 h, 1 day, and 3 dayslater. Brain sections were immunostained with an antibody against M-CSF.(A) Representative mice shown from left to right were controls (noinjury), kainic acid lesioned and sacrificed at 6 h, kainic acidlesioned and sacrificed at 24 h, and kainic acid lesioned and diedwithin 6 h. (B) Quantification of M-CSF immunoreactivity in thehippocampus after kainate injury. (C) Co-localization of M-CSF (green)and neuronal marker NeuN (red) after kainic acid lesion. (D)Illustrations of the different degrees of injury assessed by cresylviolet staining caused by kainic acid 3 days after injection and theinverse correlation with M-CSF immunoreactivity. Scale bar=200 μm in (A,C), =20 μm in (B).

FIG. 14 illustrates that M-CSF activates CREB pathway, as furtherdetailed in Example 7. (A-D) Wildtype FVB/N mice (n=4-6 per group, 2months of age) were lesioned with kainic acid (20 mg/kg, subcutaneousinjection) and treated with M-CSF (24 h before kainic acid) or PBS ascontrol. Mice were sacrificed 6 h after kainic acid injection. Onehemibrain was fixed for immunohistochemistry with an antibody againstp-CREB (A) (left and middle panels) and p-CREB immunoreactivity wasquantified as percentage of area occupied (B). The opposite hippocampiwere isolated and subjected to Western blot analysis for p-CREB (C, D)(n=4 mice/group). (E, F) Wildtype FVB/N mice were each stereotaxicallyimplanted with an ALZET brain infusion kit connected to a mini-osmoticpump filled with KG501 or DMSO (control). Two days later, M-CSF (2 hbefore KA) and KA were injected systemically. Mice were sacrificed 5days later and brain sections were analyzed for neuronal injury bycresyl violet staining (n=5 mice/group). Scale bars in (A), =200 μm inthe left panel, and 50 μm in middle and right panels; in (E), =200 μm inthe left panel, and 50 μm in the right panel. *, P<0.05; **, P<0.01compared with KA+ PBS by ANOVA and Bonferroni post-hoc test (B) or ttest (D, F).

FIG. 15 illustrates that recombinant M-CSF and IL-34 inhibit excitotoxicinjury and activate CREB pathway in vitro, as further detailed inExample 8. (A-B) B103 cells were incubated with NMDA for 24 h. MCSF (1ng/ml) and IL-34 (1 ng/ml) were added 2 h before NMDA. For inhibitorexperiments, KG501 (25 μM) or GW2580 (10 μM) was co-incubated with M-CSFor IL-34. Following incubations live and dead cells were assessed withcalcein-acetoxymethylester (CAM) and SYTOX Orange (Invitrogen),respectively. Under a fluorescence microscope, the live cells showedgreen color and the nuclei of dead cells exhibited orange fluorescence(shown in red) (A). Cell survival was expressed as the percentage oflive cells over total number of the cells (B). **, P<0.05 vs controlmedia, ##, P<0.01 vs NMDA+PBS; ANOVA, Tukey's post-hoc test. (C) B103cells were exposed to forskolin (FSK, 10 μM), IL-34 (1 or 100 ng/ml) andMCSF (1 or 100 ng/ml) for 30 min. The cells were lysed and subjected toWestern blot analysis for p-CREB. Forskolin is commonly used to raiselevels of cyclic AMP (cAMP) and used as positive control. Note thatforskolin exposure caused a prominent increase in CREB phosphorylation.Exposure to IL-34 and M-CSF caused a similar increase in CREBphosphorylation. (D-F). M-CSF and IL-34 prevent NMDA-induced cell deathand neurite dystrophy in primary neuronal culture. Primary hippocampalneurons were isolated from 16 days old CF1 mouse embryos and were agedfor 6-7 days or 21-22 days, then challenged with 100 μM NMDA in thepresence and absence of M-CSF or IL-34 (both at 10 ng/ml), and assayedfor neurotoxicity (D) or neuritic dystrophy (E-F), respectively. For theneurotoxicity assay, live and dead cells were counted according to theirmorphologies determined by phase-contrast microscopy. Results wereexpressed as % of live cells. For the neuritic dystrophy assay, cultureswere fixed and immunostained for MAP-2 to visualize dendrites.Dystrophic neurites show increased tortuosity, exhibiting multipleabrupt turns (brackets) (E). Mean differential curvature analysis inrandomly selected fields demonstrated that NMDA induced a significantincrease in neurite curvature, which was prevented by M-CSF and IL-34(n=5 fields/well) (F). Dystrophic curvature analysis was measured byblinded observers. *, P<0.05, vs culture media; #, P<0.05, ##, P<0.01,vs NMDA+PBS; ANOVA, Tukey's post-hoc test.

FIG. 16 illustrates that M-CSF as well as IL-34 inhibit NMDA-inducedcell death in B103 cells, as further detailed in Example 8. B 103neuroblastoma cells were incubated with NMDA for 24 hrs. M-CSF and IL-34were added 2 hrs before NMDA. Following incubations live and dead cellswere assessed with calcein-acetoxymethylester (CAM) and SYTOX Orange(Invitrogen), respectively. Under a fluorescence microscope, the livecells showed green color and the nuclei of dead cells exhibited orangefluorescence (shown in red). Representative images showing increasedcell death after NMDA exposure (100 μM, B) compared with control media(A), and the reduction by the treatment of M-CSF (C) and IL-34 (D). Cellsurvival was expressed as the percentage of live cells over total numberof the cells (E). Concentrations used, 1, 10 and 100 ng/ml, from left toright, for both M-CSF and IL-34. **, P<0.01 vs culture media; #, P<0.05,##, P<0.01 vs NMDA+PBS; ANOVA, Tukey's post-hoc test.

FIG. 17 illustrates that M-CSF and IL-34 prevent NMDA-induced neuritedystrophy, as further detailed in Example 8. Hippocampal neurons (21-22DIV) were exposed to culture medium (A), 100 μM NMDA (B); 100 μM NMDA+10ng/ml M-CSF (C), or 100 μM NMDA+10 ng/ml IL-34 (D). After 48 hrs,cultures were fixed and immunostained for MAP-2 to visualize dendrites.Note that NMDA exposure significantly increased tortuosity, exhibitingmultiple abrupt turns (brackets) (B), and was markedly reduced by M-CSFand IL-34 (C, D). (E) Average numbers of dystrophic neurites per neuron(n=10 fields/well). Dystrophic neurites were defined as neuritesexhibiting multiple abrupt turns (tortuosity) and were measured byblinded observers. **, P<0.01 vs culture media; ##, P<0.01 vs NMDA+PBS;ANOVA, Tukey's post-hoc test.

FIG. 18 illustrates that systemic IL-34 attenuates kainic acid-inducedneurodegeneration, as further detailed in Example 9. Two-month-old FVB/Nmice were lesioned with kainic acid (20 mg/kg, subcutaneous injection)and sacrificed 5 days later. IL-34 (100 μg/kg) was injectedintraperitoneally once 2 h before kainic acid. Kainic acid-inducedneuronal injury was assessed by cresyl violet staining (A, B), calbindin(C, D) and NeuN (E, F) immunostaining. Representative images are shownfrom hippocampi of mice treated with PBS (left) or IL-34 (right). Scalebar=200 μm. Bars in (B, D, and F) are mean±SEM (n=4 mice/group). *,P<0.05; **, P<0.01, student t test.

FIG. 19 illustrates that the systemic administration of M-CSF inhibitskainic acid-induced reporter gene activity, as further detailed inExample 10. (A-C) GFAP-luc mice (2 month of age) were lesioned withkainic acid (20 mg/kg) and bioluminescence was recorded at indicatedtime points in each mouse. Representative images showing increasedbioluminescence signals over the brain after kainic acid injury (toppanel) and the reduction by M-CSF treatment 24 h before kainic acid(bottom panel) (A). Time course of bioluminescence induction.Bioluminescence is expressed as fold induction over baseline in the micetreated with M-CSF at 2 or 24 h before kainic acid (B) or at 2 or 6 hafter kainic acid (C). Baseline was measured 1 day before kainic acidadministration for each mouse. Bars are mean±SEM (n=4-7 mice).Recombinant human M-CSF was injected intraperitoneally at 800 μg/kg bodyweight, unless otherwise specified. *, P<0.05; **, P<0.01 compared withKA+PBS by ANOVA and Bonferroni post-hoc test. (D-G) Afterbioluminescence imaging GFAP-luc mice were sacrificed (5 d afterkainate). Excitotoxic injury was assessed by cresyl violet staining (D,E) and NeuN immunostaining (F, G). Representative images are shown fromhippocampi of mice treated with PBS (left) or M-CSF (administered 2 hafter kainate, right). Scale bar=200 μm. Bars in (D and F) are mean±SEM(n=3-4 mice/group). **, P<0.01, student t test.

DETAILED DESCRIPTION

Before describing detailed embodiments of the invention, it will beuseful to set forth definitions that are utilized in describing thepresent invention.

Definitions

The practice of the present invention may employ conventional techniquesof neurochemistry, neuroscience, immunohistochemistry and molecularbiology, which are within the capabilities of a person of ordinary skillin the art. Such techniques are fully explained in the literature. Fordefinitions, terms of art and standard methods known in the art, see,for example, Sambrook and Russell “Molecular Cloning: A LaboratoryManual”, Cold Spring Harbor Laboratory Press (2001); ‘Current Protocolsin Molecular Biology’; ‘Current Protocols in Immunology’; Stanley ER“Colony stimulating factor-1”, The cytokine handbook, 1994, AcademicPress. Each of these general texts is herein incorporated by reference.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by a person of ordinaryskill in the art to which this invention belongs. The followingdefinitions are intended to also include their various grammaticalforms, where applicable. As used herein, the singular forms “a” and“the” include plural referents, unless the context clearly dictatesotherwise.

The term “macrophage colony stimulating factor receptor agonists”, asused herein, relates to biologically active, recombinant, isolatedpeptides and proteins, including their biologically active fragments,peptidomimetics and small molecules that are capable of stimulating theMacrophage colony stimulating factor receptor, M-CSFR or c-fms. M-CSFRagonists are also referred to as c-fms ligands herein.

The terms “M-CSF”, “macrophage colony stimulating factor”, “CSF-1”,“CSF1”, “colony stimulating factor1” and “colony stimulating factor-1”are used interchangeably herein.

The term “subject”, as used herein, refers to an animal, preferably amammal, including mouse, rabbit, dog, cat, guinea pig, goat, cow, horse,pig, sheep, monkey, primate, ape, and human.

The term “cognitive function”, as used herein, refers to a subject'sability to store and retrieve memories, learn, communicate and/orfunction independently.

The term “therapeutic effect”, as used herein, refers to a consequenceof treatment that might intend either to bring remedy to an injury thatalready occurred or to prevent an injury before it occurs. A therapeuticeffect may include, directly or indirectly, the reduction of neuronaldamage and the stimulation of neuronal repair following acute or chronicinjury of nerve cells. A therapeutic effect may also include, directlyor indirectly, the arrest, reduction, or elimination of the progressionof neuronal cell death following acute or chronic injury of nerve cells.Furthermore, a therapeutic effect may include, directly or indirectly,the prevention or reduction of neuronal damage prior to acute or chronicinjury of nerve cells.

The term “therapeutically effective amount” of a macrophage colonystimulating factor receptor agonist is an amount that is sufficient toprovide a therapeutic effect in a mammal, including a human. Naturally,dosage levels of the particular macrophage colony stimulating factorreceptor agonist employed to provide a therapeutically effective amountvary in dependence of the type of injury, the age, the weight, thegender, the medical condition of the mammal/human, the severity of thecondition, the route of administration, and the particular macrophagecolony stimulating factor receptor agonist employed. Therapeuticallyeffective amounts of a macrophage colony stimulating factor receptoragonist, as described herein, can be estimated initially from cellculture and animal models. For example, IC₅₀ values determined in cellculture methods can serve as a starting point in animal models, whileIC₅₀ values determined in animal models can be used to find atherapeutically effective dose in humans.

The term “recombinant”, as used herein, relates to a protein orpolypeptide that is obtained by expression of a recombinantpolynucleotide.

The terms “isolated” and “purified” relate to molecules that have beenmanipulated to exist in a higher concentration or purer form thannaturally occurring.

The term “pharmaceutical composition”, as used herein, refers to amixture of at least one macrophage colony stimulating factor receptoragonist with chemical components such as diluents or carriers that donot cause unacceptable adverse side effects and that do not prevent themacrophage colony stimulating factor receptor agonist(s) from exerting atherapeutic effect. A pharmaceutical composition serves to facilitatethe administration of the macrophage colony stimulating factor receptoragonist(s).

Neuronal Viability, Repair and Protection; Neuronal Death

The term “attenuating neuronal damage”, as used herein, refers to themacrophage colony stimulating factor receptor agonists' ability toreduce neuronal death and to protect neurons of the central nervoussystem, in vitro as well as in vivo, from neuronal death, both inquality and quantity, when compared to a negative control compound orvehicle that does not attenuate neuronal damage.

The term “stimulating neuronal repair”, as used herein, refers to themacrophage colony stimulating factor receptor agonists' ability torestore neuronal viability and function following a neuronal injury orinsult. Neuronal viability is maintained through a complex network ofsignaling pathways that can be disturbed in response to a wide varietyof cellular stress.

Neuronal insults due to traumatic brain injury, cerebral ischemia,glucose deprivation or degenerative disease cause an upregulation in theexpression of neuroprotective factors and their receptors in an array ofcells that are involved in the neuronal repair process, includingastrocytes and microglia, macrophages, mastcells and other invadinginflammatory cells, T cells and certain neurons (Sofroniew et al.,2001).

The mitogen-activated protein (MAP) kinases and phosphatidylinositol-3kinase (PI3K) are serine/threonine protein kinases that play criticalroles in neuronal growth, differentiation and survival. Activation ofthe ERK or p42/p44 MAP kinase members of the MAP kinase family andactivation of the PI3K Akt signaling pathway promote cell survival,while stress-activated protein kinases (SAPK's), c-Jun N-terminalkinases (JNK's) and the p38 MAP kinase (p38 MAPK), which are alsomembers of the MAP kinase family, facilitate cell death (Morrison etal., 2002).

Many neuroprotective factors such as nerve growth factor (NGF),brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3),neurotrophin-4 (NT-4), novel neurotrophin-1 (NNT-1) or insulin-likegrowth factor 1 (IGF-1) exert their actions through a particularsignaling pathway. Nerve growth factor (NGF) is critical for thesurvival and maintenance of sympathetic and sensory neurons. Uponrelease from its target neurons, NGF binds to and activates its highaffinity receptor TrkA on the target neurons and is internalized intothe responsive neurons; NGF might also act through the p75 receptor (akalow-affinity nerve growth factor receptor, LNGFR). BDNF is expressed inthe brain and in some peripheral tissues and supports the survival ofexisting neurons as well as stimulates neurogenesis both in the centraland peripheral nervous system. It exerts its action through the TrkB andp75 receptors. NT-3 aids in the survival of existing neurons andsupports neurogenesis both in the peripheral and central nervous system.It exerts its action through the TrkB, TrkC and p75 receptors. NT-4 hassimilar functions like NT-3 and activates primarily the TrkB receptor.IGF-1, in its function as neurotrophic factor, helps in the survival ofneurons and acts through the stimulation of the IGF-1 receptor. p75(LNGFR) belongs to a family of receptors that includes CD27, CD30, CD40,OX40, Fas (CD95), and the tumor necrosis factor receptors (TNF-R). Allthese family members are able to control cell viability through theregulation of apoptosis (Sofroniew et al., 2001). The Trk receptorfamily (TrkA, TrkB and TrkC) as well as the IGF-1 receptor are receptortyrosine kinases and act via the PI3K Akt signaling pathway, whichinvolves activation of the cAMP responsive elements binding protein,CREB.

CREB belongs to a family of proteins that function as transcriptionfactors. It is expressed in all cells of the central nervous system andis assumed to play a key role in the protection of neurons and inneuronal survival following neuronal damage (Walton & Dragunow, 2000).CREB activation has been implicated in the resistance of neuronal cellsto various injuries and insults, but there is now evidence that the Aktsignaling pathway could lead to CREB activation (Morrison et al., 2002).CREB signaling also appears to play a major role in mediating M-CSF'sbiological effects in macrophages (Casals-Casas et al., 2009).Furthermore, kainic acid injury was shown to selectively decreasephosphorylation of CREB (phospho-CREB) in vulnerable regions (Ferrer etal., 2002).

Neuronal cell death as a consequence of apoptotic or necrotic events canbe caused in acute and chronic ways through neuronal damage andneuroinflammation. Acute neuronal injury and acute neurodegeneration canbe caused by a traumatic brain injury due to a sudden, violent insult,by cerebral ischemia due to restricted blood supply, glucosedeprivation, oxidative stress through free radicals or spinal cordinjury. Neurodegenerative diseases of the central nervous system (CNS)such as Alzheimer's disease, Parkinson's disease, Amyotrophic LateralSclerosis and Huntington's disease lead to chronic neurodegeneration.Excitotoxic injury (excitatory amino acid neurotoxic injury) followingoverstimulation of the glutamate receptors, the NMDA receptor or theAMPA receptor, by the neurotransmitter glutamate or molecules with asimilar effect (so-called excitotoxins), such as N-methyl D-aspartate(NMDA) or kainic acid, may be involved in both acute and chronicneurodegenerative events.

Alzheimer's disease is characterized by progressive memory loss andcognitive dysfunction; neuropathological changes that are assessedpost-mortem include amyloid plaques, neurofibrillary tangles,neuroinflammation and microvascular changes (Querfurth & LaFerla, 2010).

Parkinson's disease is a degenerative disorder of the central nervoussystem that primarily impairs motor skills and speech. These symptomsresult from decreased stimulation of the motor cortex due toinsufficient production of dopamine in dopaminergic neurons of thebrain. It is assumed that the presence of Lewy bodies contributes to thegradual death of brain cells and tissue.

Huntington's disease is a progressive, neurodegenerative, geneticallybased disorder that results from brain damage caused by aggregats ofmisfolded huntingtin protein and that affects muscle coordination andcognitive functions, typically from middle age on.

Amyotrophic Lateral Sclerosis is characterized by the degeneration ofupper and lower motor neurons with the ultimate disability to initiateand control voluntary movement.

Dosages, Dosing Regimens, Formulations and Administration of MacrophageColony Stimulating Factor Receptor Agonists

The dosage and dosing regimen for the administration of a macrophagecolony stimulating factor receptor agonist for attenuating neuronaldamage and for stimulating neuronal repair, as provided herein, isselected by one of ordinary skill in the art, in view of a variety offactors including, but not limited to, age, weight, gender, and medicalcondition of the subject, the severity of the neuronal damage that isexperienced, the route of administration (oral, systemic, local), thedosage form employed, and may be determined empirically using testingprotocols, that are known in the art, or by extrapolation from in vivoor in vitro tests or diagnostic data.

The dosage and dosing regimen for the administration of a macrophagecolony stimulating factor receptor agonist, as provided herein, is alsoinfluenced by toxicity in relation to therapeutic efficacy. Toxicity andtherapeutic efficacy can be determined according to standardpharmaceutical procedures in cell cultures and/or experimental animals,including, for example, determining the LD50 (the dose lethal to 50% ofthe population) and the ED50 (the dose therapeutically effective in 50%of the population). The dose ratio between toxic and therapeutic effectsis the therapeutic index and it can be expressed as the ratio LD50/ED50.Molecules that exhibit large therapeutic indices are generallypreferred.

The effective dose of a macrophage colony stimulating factor receptoragonist, can, for example, be less than 50 mg/kg of subject body mass,less than 40 mg/kg, less than 30 mg/kg, less than 20 mg/kg, less than 10mg/kg, less than 5 mg/kg, less than 3 mg/kg, less than 1 mg/kg, lessthan 0.3 mg/kg, less than 0.1 mg/kg, less than 0.05 mg/kg, less than0.025 mg/kg, or less than 0.01 mg/kg. Effective doses of a macrophagecolony stimulating factor receptor agonist, administered to a subject asprovided in the methods herein can, for example, be between about 0.001mg/kg to about 50 mg/kg. In certain embodiments, the effective dose isin the range of, for example, 0.005 mg/kg to 10 mg/kg, from 0.01 mg/kgto 2 mg/kg, or from 0.05 mg/kg to 0.5 mg/kg. In various embodiments, aneffective dose is less than 1 g, less than 500 mg, less than 250 mg,less than 100 mg, less than 50 mg, less than 25 mg, less than 10 mg,less than 5 mg, less than 1 mg, less than 0.5 mg, or less than 0.25 mgper dose, which dose may be administered once, twice, three times, orfour or more times per day. In certain embodiments, an effective dosecan be in the range of, for example, from 0.1 mg to 1.25 g, from 1 mg to250 mg, or from 2.5 mg to 1000 mg per dose. The daily dose can be in therange of, for example, from 0.5 mg to 5 g, from 1 mg to 1 g, or from 3mg to 300 mg.

In some embodiments, the dosing regimen is maintained for at least oneday, at least two days, at least about one week, at least about twoweeks, at least about three weeks, at least about one month, or longer.In some embodiments, an intermittent dosing regimen is used, i.e., oncea month, once every other week, once every other day, once per week,twice per week, and the like. In some embodiments, the compound isadministered at least once daily for at least five consecutive days.

Routes of administration of macrophage colony stimulating factorreceptor agonists or pharmaceutical compositions containing macrophagecolony stimulating factor receptor agonists may include, but are notlimited to, oral, nasal and topical administration and intramuscular,subcutaneous, intravenous, intraperitoneal or intracerebral injections.The macrophage colony stimulating factor receptor agonists orpharmaceutical compositions containing macrophage colony stimulatingfactor receptor agonists may also be administered locally via aninjection or in a targeted delivery system.

The macrophage colony stimulating factor receptor agonist may beadministered in a single daily dose, or the total daily dose may beadministered in divided doses, two, three, or more times per day.Optionally, in order to reach a steady-state concentration in the brainquickly, an intravenous bolus injection of the macrophage colonystimulating factor receptor agonist can be administered followed by anintravenous infusion of the macrophage colony stimulating factorreceptor agonist.

The macrophage colony stimulating factor receptor agonist can beadministered to the subject as a pharmaceutical composition thatincludes a therapeutically effective amount of the macrophage colonystimulating factor receptor agonist in a pharmaceutically acceptablevehicle. It can be incorporated into a variety of formulations fortherapeutic administration by combination with appropriatepharmaceutically acceptable carriers or diluents, and may be formulatedinto preparations in solid, semi-solid, liquid, or gaseous forms, suchas tablets, capsules, powders, granules, ointments, solutions,suppositories, injections, inhalants, gels, microspheres, and aerosols.

In some embodiments, the macrophage colony stimulating factor receptoragonist can be formulated as a delayed release formulation. Suitablepharmaceutical excipients and unit dose architecture for delayed releaseformulations may include those described in U.S. Pat. Nos. 3,062,720 and3,247,066. In other embodiments, the macrophage colony stimulatingfactor receptor agonist can be formulated as a sustained releaseformulation. Suitable pharmaceutical excipients and unit dosearchitecture for sustained release formulations include those describedin U.S. Pat. Nos. 3,062,720 and 3,247,066. The macrophage colonystimulating factor receptor agonist can be combined with a polymer suchas polylactic-glycoloic acid (PLGA), poly-(I)-lactic-glycolic-tartaricacid (P(I)LGT) (WO 01/12233), polyglycolic acid (U.S. Pat. No.3,773,919), polylactic acid (U.S. Pat. No. 4,767,628),poly(ε-caprolactone) and poly(alkylene oxide) (U.S. 20030068384) tocreate a sustained release formulation. Such formulations can be used inimplants that release an agent over a period of several hours, a day, afew days, a few weeks, or several months depending on the polymer, theparticle size of the polymer, and the size of the implant (see, e.g.,U.S. Pat. No. 6,620,422). Other sustained release formulations aredescribed in EP 0 467 389 A2, WO 93/241150, U.S. Pat. No. 5,612,052, WO97/40085, WO 03/075887, WO 01/01964A2, U.S. Pat. No. 5,922,356, WO94/155587, WO 02/074247A2, WO 98/25642, U.S. Pat. Nos. 5,968,895,6,180,608, U.S. 20030171296, U.S. 20020176841, U.S. Pat. Nos. 5,672,659,5,893,985, 5,134,122, 5,192,741, 5,192,741, 4,668,506, 4,713,244,5,445,832 4,931,279, 5,980,945, WO 02/058672, WO 9726015, WO 97/04744,and. US20020019446. In such sustained release formulationsmicroparticles of drug are combined with microparticles of polymer.Additional sustained release formulations are described in WO 02/38129,EP 326 151, U.S. Pat. No. 5,236,704, WO 02/30398, WO 98/13029; U.S.20030064105, U.S. 20030138488A1, U.S. 20030216307A1,U.S. Pat. No.6,667,060, WO 01/49249, WO 01/49311, WO 01/49249, WO 01/49311, and U.S.Pat. No. 5,877,224.

Pharmaceutical compositions can include, depending on the formulationdesired, pharmaceutically-acceptable, non-toxic carriers of diluents,which are defined as vehicles commonly used to formulate pharmaceuticalcompositions for animal or human administration. The diluent is selectedso as not to affect the biological activity of the combination. Examplesof such diluents are distilled water, buffered water, physiologicalsaline, PBS, Ringer's solution, dextrose solution, and Hank's solution.In addition, the pharmaceutical composition or formulation can includeother carriers, adjuvants, or non-toxic, nontherapeutic, nonimmunogenicstabilizers, excipients, and the like. The compositions can also includeadditional substances to approximate physiological conditions, such aspH adjusting and buffering agents, toxicity adjusting agents, wettingagents, and detergents. The composition can also include any of avariety of stabilizing agents, such as an antioxidant for example.Tablet formulations can comprise a sweetening agent, a flavoring agent,a coloring agent, a preservative, or some combination of these toprovide a pharmaceutically elegant and palatable preparation.

Further guidance regarding formulations that are suitable for varioustypes of administration can be found in Remington's PharmaceuticalSciences, Mace Publishing Company, Philadelphia, Pa., 20th ed. (2000).

Formulations suitable for parenteral administration include aqueous andnon-aqueous, isotonic sterile injection solutions, which can containantioxidants, buffers, bacteriostats, and solutes that render theformulation isotonic with the blood of the intended recipient, andaqueous and non-aqueous sterile suspensions that can include suspendingagents, solubilizers, thickening agents, stabilizers, and preservatives.

The components used to formulate the pharmaceutical compositions arepreferably of high purity and are substantially free of potentiallyharmful contaminants (e.g., at least National Food (NF) grade, generallyat least analytical grade, and more typically at least pharmaceuticalgrade). Moreover, compositions intended for in-vivo use are usuallysterile. To the extent that a given compound must be synthesized priorto use, the resulting product is typically substantially free of anypotentially toxic agents, particularly any endotoxins, which may bepresent during the synthesis or purification process. Compositions forparental administration are also sterile, substantially isotonic andmade under GMP conditions.

Macrophage colony stimulating factor receptor agonists or pharmaceuticalcompositions containing macrophage colony stimulating factor receptoragonists may be administered to a subject using any convenient meanscapable of resulting in the desired treatment of neuronal damage andstimulation of neuronal repair. Routes of administration include, butare not limited to, oral, rectal, parenteral, intravenous, intracranial,intraperitoneal, intradermal, transdermal, intrathecal, intranasal,intracheal, intracapillary, subcutaneous, subdermal, topical,intramuscular, injection into the cerebrospinal fluid, injection intothe intracavity, or injection directly into the brain. Oraladministration can include, for instance, buccal, lingual, or sublingualadministration. The macrophage colony stimulating factor receptoragonists may be systemic after administration or may be localized by theuse of local administration, intramural administration, or use of animplant that acts to retain the active dose at the site of implantation.For a brief review of methods for drug delivery see Langer, 1990.

Macrophage Colony Stimulating Factor (M-CSF, CSF-1)

Monocytes, macrophages, natural killer (NK) cells, and polymorphonuclearneutrophils (PMN) are part of a subject's innate immune system, whichgenerally acts as the initial defense against foreign cells.

Macrophage colony-stimulating factor (M-CSF), also known ascolony-stimulating factor-1 (CSF-1) and initially described as a growthfactor of the mononuclear phagocytic lineage, is a secreted cytokinewhich influences hematopoietic stem cells to differentiate intomacrophages or other related cell types and which regulates thesurvival, proliferation, differentiation, and chemotaxis of cells of themonocyte/macrophage lineage (Hamilton, 2008; Pixley and Stanley, 2004).M-CSF is produced by multiple cell types including monocyte/macrophages,endothelial cells, fibroblasts, and bone marrow stromal cells (Chitu andStanley, 2006; Hamilton, 2008; Pixley and Stanley, 2004).

Macrophage Colony Stimulating Factor Receptor (M-CSFR)

The biological effects of M-CSF are mediated by a single M-CSF receptor(M-CSFR), a ligand inducible protein tyrosine kinase receptor, which isencoded by the c-fms proto-oncogene (Sherr et al., 1985). M-CSFR ispredominantly expressed in mononuclear phagocytes and to a lesser extentin oocytes, trophoblasts, and certain lymphocytes (Chitu and Stanley,2006; Hamilton, 2008; Pixley and Stanley, 2004). Ligand binding toM-CSFR triggers multiple signal transduction pathways resulting inactivation of the protein kinase AKT, the cAMP-response-element-bindingprotein (CREB) and mitogen-activated protein (MAP) kinase (Hamilton,1997; Pixley and Stanley, 2004).

Consistent with its role in regulating the monocyte/macrophage lineage,in the central nervous system M-CSFR is expressed in microglia (Raivichet al., 1998) and the presence of M-CSF is crucial for maturation ofthese cells (Imai and Kohsaka, 2002).

Macrophage Colony Stimulating Factor Receptor Agonists

The present invention provides methods for attenuating neuronal damageand stimulating neuronal repair using compounds that stimulate c-fms(macrophage colony stimulating factor receptor agonists or ligands)following acute or chronic injury of nerve cells of the central nervoussystem. Macrophage colony stimulating factor receptor agonists stimulatethe macrophage colony stimulating factor receptor, M-CSFR or also calledc-fms, and may be biologically active, recombinant, isolated peptidesand proteins, including their biologically active fragments,peptidomimetics or small molecules. In certain embodiments, suchcompounds are orally active and can cross the blood brain barrier.

Macrophage colony stimulating factor receptor agonists can be identifiedexperimentally using a variety of in vitro and/or in vivo models.Isolated macrophage colony stimulating factor receptor agonists can bescreened for binding to various sites of the purified macrophage colonystimulating factor receptor proteins. Compounds can also be functionallyscreened for their ability to exert neuroprotective effects using invitro culture systems. In addition, compounds can be evaluated aspotential neuroprotective factors and for treatment or prevention ofneuronal death, including cognitive impairment, using animal models(e.g., monkey, rat, or mouse models). Candidate compounds that exertneuroprotective effects may also be identified by known pharmacology,structure analysis, or rational drug design using computer basedmodeling.

Candidate compounds that exert neuroprotective effects may encompassnumerous chemical classes, though typically they are organic molecules,preferably small organic compounds having a molecular weight of morethan 50 and less than about 2,500 daltons. They may comprise functionalgroups necessary for structural interaction with proteins (e.g.,hydrogen bonding), and typically include at least an amine, carbonyl,hydroxyl, or carboxyl group. They often comprise cyclical carbon orheterocyclic structures and/or aromatic or polyaromatic structuressubstituted with one or more functional groups. They may be found amongbiomolecules including peptides, saccharides, fatty acids, steroids,purines, and pyrimidines, and structural analogs thereof.

Candidate compounds that exert neuroprotective effects can besynthesized or isolated from natural sources (e.g., bacterial, fungal,plant, or animal extracts). The synthesized or isolated candidatecompound may be further chemically modified (e.g., acylated, alkylated,esterified, or amidified), or substituents may be added (e.g.,aliphatic, alicyclic, aromatic, cyclic, substituted hydrocarbon, halo(especially chloro and fluoro), alkoxy, mercapto, alkylmercapto, nitro,nitroso, sulfoxy, sulfur, oxygen, nitrogen, pyridyl, furanyl,thiophenyl, or imidazolyl substituents) to produce structural analogs,or libraries of structural analogs (see, for example, U.S. Pat. Nos.5,958,792; 5,807,683; 6,004,617; 6,077,954). Such modification can berandom or based on rational design (see, for example, Cho et al., 1998;Sun et al., 1998).

In the working examples human M-CSF protein as well as murineInterleukin-34 protein, both in isolated, purified and/or recombinantform, were utilized as macrophage colony stimulating factor receptoragonists. Such macrophage colony stimulating factor receptor agonistsmay be administered locally at or near a site of injury within thecentral nervous system or systemically in a therapeutically effectiveamount and within a time period following acute or chronic injury thatis sufficient to provide a therapeutic effect.

Attenuating Neuronal Damage and Stimulating Neuronal Repair

The present invention provides methods for attenuating neuronal damageand stimulating neuronal repair following acute or chronic injury ofnerve cells of the central nervous system. Furthermore, the presentinvention provides methods for preventing or attenuating neuronal damageprior to chronic injury of nerve cells of the central nervous system.Without intending to be limited by any theory or mechanism of action, itis demonstrated in the examples provided herein that the administrationof M-CSF, aka CSF-1, as well as IL-34, both macrophage colonystimulating factor receptor agonists, in various mouse models ofneurodegeneration can improve cognitive function, attenuate neuronaldamage and/or stimulate neuronal repair. Of crucial importance, themacrophage colony stimulating factor receptor agonists were demonstratedto exert the neuroprotective effects not only when administered before aneuronal insult had occurred, but also following a neuronal insult.

As described in example 1, doses of M-CSF administered to hAPP mice (awell-established mouse model of Alzheimer's disease) improved cognitivefunction. The administration of M-CSF attenuated neuronal damage in amouse model of kainic acid-induced neurodegeneration (example 2) andkainic acid-induced microgliosis (example 3), The significance ofneuronal M-CSF receptor signaling for neuronal protection and repair wasdemonstrated in examples 4, 5, and 6 and an involvement of the cAMPresponsive element binding protein (CREB) pathway shown in example 7. Inexample 8, M-CSF and IL-34 are shown to exert neuroprotective effects incultured neurons against excitotoxic injury. Examples 9 and 10 describethe neuroprotective effects of IL-34 and M-CSF, respectively, in micefollowing neuronal injury.

Macrophage colony stimulating factor receptor agonists demonstratedneuroprotective effects in vivo, when administered to mice either prioror after neuronal injury.

As detailed in Example 2, recombinant human macrophage colonystimulating factor receptor agonist M-CSF was administered systemicallyin a mouse model of kainic acid-induced neurodegeneration to explorewhether systemically administered M-CSF had neuroprotective effects.Subcutaneous injection of kainic acid into wildtype FVB mice resulted insignificant degeneration of neurons in the pyramidal layer (see FIG. 3A) and reduced hippocampal calbindin immunereactivity (see FIG. 3 C). Incontrast, wildtype FVB mice that systemically had been treated withrecombinant, human M-CSF 24 h prior to kainic acid administration showedlittle hippocampal cell loss (see FIG. 3 A and B) and calbindinreduction (see FIG. 3 C and D). In conclusion, the systemicadministration of recombinant, human M-CSF attenuated kainicacid-induced excitotoxic injury and provided significant neuroprotectionin vivo in FVB mice.

As detailed in Example 10, recombinant human M-CSF exerted strongneuroprotective effects in mice, even if administered up to 6 h after aneurotoxic insult. Mice receiving recombinant human M-CSF at 2 or 6hours after kainic acid injection showed similar and significantreduction of astrogliosis (see FIG. 19). Reduced neurodegeneration inthese mice was confirmed by pathological analysis (data not shown).These results demonstrate that recombinant human M-CSF exerts strongneuroprotective effects, even if administered up to 6 h after aneurotoxic insult.

Interleukin-34, a cytokine which facilitates the growth and survival ofmonocytes, has been reported to elicit its activity through binding ofc-fms (Lin et al., 2008). In cultured macrophages IL-34 shows anability, equivalent to M-CSF, to support cell growth and survival. Itmay, however, interact with distinct regions of c-FMS that might bedifferent from the regions M-CSF interacts with and IL-34 might initiatedifferent biological activities and signal activation (Chihara et al.,2010; Wei et al., 2010).

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentinvention. Any recited method can be carried out in the order of eventsrecited or in any other order which is logically possible. In thefollowing, experimental procedures and examples will be described toillustrate parts of the invention.

Experimental Procedures

The following methods and materials were used in the examples that aredescribed further below.

Mice. The following transgenic mouse lines were used: hAPP mice (line41) expressing mutated (London V717I and Swedish K670M/N671L) humanAPP751 under the control of the murine Thy1 promoter (Rockenstein etal., 2001), GFAP-luc mice (Caliper Life Science) (Zhu et al., 2004),op/op mice (Wiktor-Jedrzejczak et al., 1990; Yoshida et al., 1990) (TheJackson's Laboratory), actin-GFP (ACTB-EGFP) mice expressing enhancedgreen fluorescence protein (EGFP) under the control of a chicken β-actinpromoter (Okabe et al., 1997) (The Jackson's Laboratory), CaMKIIα-cremice (kindly obtained from Dr. Rudolf Jaenisch, Massachusetts Instituteof Technology) (Fan et al., 2001), c-fms-iCre mice (Deng et al., 2010),ROSA-stop^(flox)-CFP mice (Srinivas et al., 2001), c-fms^(f/f)(loxP-c-fms-loxP) mice (Li et al., 2006) and c-fms knockout mice (Li etal., 2006). c-fms^(f/f) mice were crossed with CaMKIIα-cre mice togenerate c-Fms-null mutant mice (c-fms^(f/f)-cre). c-Fms reporter(Csf1r-EGFP, macrophage Fas induced apoptosis, MAFIA) mice (Burnett etal., 2004), expressing EGFP under control of the c-fms promoter, werepurchased from the Jackson Laboratory under agreement with AriadPharmaceuticals (Cambridge, Mass.). The hAPP, c-fms^(f/f), CaMKIIα-creand MAFIA mice were on C57bl/6 genetic background, and GFAP-luc micewere on FVB/N background. Wildtype FVB/N or C57bl/6 mice were purchasedfrom The Jackson's Laboratory. Mice were 2-3 month of age at thebeginning of experiments, except for hAPP mice which were 5.5-6.5 or18-20-month-old. Animal handling was performed in accordance withinstitutional guidelines and approved by a local IACUC. All experimentswere done in a randomized and blinded fashion.

Kainic acid administration. For FVB/N mice, kainic acid (Tocris,Ellisville, Mo.) was dissolved in distilled water and injectedsubcutaneously (20 or 30 mg/kg) to induce neurodegeneration (Luo et al.,2006). Seizure activity was monitored every 15 min for 1 h after kainateadministration, using a scoring system from 0 to 8 with 0 showing nobehavioral changes and 8 showing death (Janumpalli et al., 1998). Allkainic acid-injected mice reached at least stage 3. For C57Bl/6 mice,kainic acid (0.50 μl; 0.1 μg/μl) was injected stereotaxicallyunilaterally into the right dorsal hippocampus (coordinates from bregma:A=−2.0 mm and L=−1.8 mm, from brain surface: H=−2.0 mm) under Isofluraneanesthesia.

Kainic acid was injected over 2 min using a 5-μl Hamilton syringe. Afterinjection, the needle was maintained in situ for an additional 2 min. tolimit reflux along the injection track. The skin was closed usingadhesive Surgicalblock and each mouse was injected subcutaneously withBuprenex as directed for pain relief. Animals were examined 1-5 daysafter kainic acid injection.

Treatment with recombinant macrophage colony stimulating factor receptoragonists. Recombinant human M-CSF was provided by Biogen Idec (BiogenIdec, Cambridge, Mass.). Recombinant mouse IL-34 was purchased from R&DSystems. M-CSF was injected intraperitoneally at 800 μg/kg body weight,a dose previously used clinically in bone marrow transplantationpatients (Nemunaitis et al., 1993), or, as indicated. IL-34 was injectedintraperitoneally at 100 μg/kg body weight. The same volume of PBS wasused as a control treatment. KG501 was purchased from Sigma-Aldrich (St.Louis, Mo.) and dissolved in dimethyl sulfoxide (DMSO). For hAPP mice,recombinant human M-CSF was injected intraperitoneally 3 times a week at800 μg/kg body weight, a dose previously used clinically in bone marrowtransplantation patients (Nemunaitis et al., 1993). The same volume ofPBS was used as a control treatment. Kainic acid-injured mice receivedone injection of recombinant human M-CSF at 800 μg/kg body weight unlessindicated otherwise.

Behavioral Tests for hAPP mice. The Morris Water Maze (MWM) was used toassess the effect of M-CSF on spatial learning and memory (Adlard etal., 2005). Briefly, after training the mice with a visible platform,animals were subjected to 6 days of place discrimination training usinga hidden platform, with four trials per day, followed by a probe trial24 hr later to assess retention of the task. Data was analyzed using theEthovision automated tracking system (Noldus Information Technology).There was no significant difference in the swim speed between thedifferent groups of animals across the study.

Osmotic minipump implantation. Mice were anesthetized with isofluorane.Osmotic minipumps (model 2001, duration: 1 wk; Alzet, Cupertino, Calif.)filled with KG501 (1 μl/h, 250 μg/μl, dissolved in DMSO) or DMSO alone,were implanted subcutaneously into the back of wildtype FVB/N mice, andconnected to a brain infusion kit that was placed stereotactically inthe right lateral ventricle (coordinates from bregma: A=−0.14 mm,L=−0.76 mm; from brain surface: H=−2.5 mm). Two days after implantation,KA (20 mg/kg) was injected subcutaneously. M-CSF was injected (800 μg/kgbody weight, i.p.) 2 h before KA. Continuous substance applicationthrough the minipump lasted for 5 more days, and then the mice wereanesthetized and perfused.

Tissue processing. Mice were anesthetized with 400 mg/kg chloral hydrate(Sigma-Aldrich) and transcardially perfused with 0.9% saline (Luo etal., 2007; Luo et al., 2006). Brains were removed and divided sagitally.One hemibrain was postfixed in phosphate-buffered 4% paraformaldehyde,pH 7.4, at 4° C. for 48 h and sectioned at 40 μm with a Vibratome 2000(Leica, Allendale, N.J.) and stored in cryoprotective medium; the otherhemibrain was snap frozen and stored at −80° C. for biochemical analysis(Luo et al., 2007; Luo et al., 2006).

Determination of cerebral Aβ Levels by ELISA immunoassay analysis.Snap-frozen hippocampi and cortices were homogenized in RIPA bufferfollowed by 70% formic acid at 0.1 mg weight tissue per 1 ml. A13peptides were quantified by ELISA, as described previously (Pickford etal., 2008) using antibody 266 (5 μg/ml, Aβ₁₃₋₂₈; Elan Pharmaceuticals)as the capture antibody for total Aβ_(1-x), or antibody 21F12 (5 μg/ml,Aβ₃₇₋₄₂; Elan Pharmaceuticals) as the capture antibody for Aβ_(x-42) andbiotinylated 3D6 (2 μg/ml, Aβ₁₋₅; Elan Pharmaceuticals) as the detectionantibody. After incubation with the secondary antibody, samples wereincubated with avidin-HRP (diluted 1:4,000; Vector Laboratories), andthe signal was developed using 1-step Turbo™B ELISA solution (PierceBiotechnology).

Western blotting. Snap-frozen hippocampi were lysed in 200 μl RIPA lysisbuffer (500 mM Tris, pH 7.4, 150 mM NaCl, 0.5% sodium deoxycholate, 1%NP-40, 0.1% SDS and complete protease inhibitors (Roche) (Lin et al.,2005). Cell lysates (20 μl) were mixed with 4× NuPage LDS loading buffer(Invitrogen) and loaded on a 3-12% SDS-polyacrylamide gradient gel andsubsequently transferred onto a PVDF membrane. The blot was incubatedwith rabbit polyclonal antibodies against p-CREB (1:500) or c-fms(1:200), and a horseradish peroxidase-conjugated secondary antibody(Amersham, Pharmacia Biotech, Piscataway, N.J.). Protein signals weredetected using an ECL kit (Amersham Pharmacia Biotech).

Cresyl Violet staining. Brain sections were mounted on Superfrost plusslides (Fisher Scientific, Pittsburgh, Pa.), air-dried, rehydrated,stained with 0.02% Cresyl Violet (Sigma) in acetate buffer (pH 3.2),then dehydrated through a series of alcohols, cleared in xylene andcoverslipped (Luo et al., 2006). Neuronal damage/loss was assessed basedon the appearance of gaps or thinning and disappearance of the Niss1substance in the CA1 and CA3 pyramidal cell layers. The lesion area wasquantified with Metamorph Imaging software (Molecular Devices,Downington, Pa.).

Immunohistochemistry, image analysis and confocal microscopy.Immunohistochemistry was performed on free-floating sections followingstandard procedures (Luo et al., 2007; Luo et al., 2006). Primaryantibodies were against: Calbindin (1:10,000, Millipore, Billerica,Mass.), CD68 (1:50, Serotec, Raleigh, N.C.), Iba-1 (1:2,500, WakoChemicals, Richmond, Va.), Cdllb (1:200, Abcam, Cambridge, Mass.),Neuropeptide Y (1:200; Millipore, Billerica, Mass.), M-CSF (1:2000, R &D Systems, Minneapolis, Minn.), p-CREB (Ser 133) (1:1000, Millipore,Billerica, Mass.), EGFP (1:1,000, Invitrogen, Carlsbad, Calif.) and 3D6(biotinylated; Elan Pharmaceuticals, South San Francisco, Calif.). Sixanti-c-Fms antibodies were obtained (Santa Cruz, Catalog # SC-31638 andSC-33358; Upstate/Millipore, Catalog #06-174 and 06-457; Cell SignalingTechnology, Catalog #3155; Biogen, generated by New England Peptide,sequence Ac-DPESPGSTC-amide) and tested with brain sections from c-fmsknockout mice (Li et al., 2006). After overnight incubation, primaryantibody staining was revealed using biotinylated secondary antibodiesand the ABC kit (Vector, Burlingame, Calif.) with Diaminobenzidine (DAB,Sigma-Aldrich) or fluorescence conjugated secondary antibodies. Theimmunoreactivity was quantified as the percent area covered by Metamorphsoftware (Molecular Devices, Sunnyvale, Calif.), as previously described(Luo et al., 2007; Luo et al., 2006). For each staining, a total ofthree hippocampal brain sections per mouse were analyzed. Colocalizationof two antigens was analyzed under a confocal microscope (LSM 510, CarlZeiss, Thornwood, N.Y.) using LSM Image Browser software (Carl Zeiss).

Parabiosis. Actin-GFP mice were parabiosed with wildtype littermates orhAPP transgenic mice, as previously described (Conboy et al., 2005).Pairs of mice were anesthetized and prepared for surgery. Mirror-imageincisions at the left and right flanks, respectively, were made throughthe skin. Shorter (˜1 cm) incisions were made through the abdominalwall. The abdominal openings were sutured together, and the skin of eachmouse was stapled (9 mm Autoclip, Clay Adams) to the skin of itsparabiont, thereby closing the incision. Each mouse was injectedsubcutaneously with Baytril antibiotic and Buprenex, as directed forpain and monitored during recovery. Blood circulation was establishedafter about 2 wks, and the mice were analyzed at 6 wks after surgery. Tostudy the effects of M-CSF, M-CSF or PBS as control was administeredseparately into both parabionts starting at week 2. hAPP parabiontsreceived M-CSF for 4 weeks. For kainic acid injury, actin-GFP mice werecrossed with FVB/N mice to increase susceptibility to kainic acid and F1mice were used for experiments. M-CSF was injected (i.p.) 24 h beforekainic acid.

In Vivo bioluminescence imaging. Bioluminescence was detected with theIn Vivo Imaging System (Lin et al., 2005; Luo et al., 2007; Luo et al.,2006) (IVIS Spectrum; Caliper Life Science, Alameda, Calif.). Mice wereinjected intraperitoneally with 150 mg/kg D-luciferin (Xenogen) 10 minbefore imaging and anesthetized with isofluorane during imaging. Photonsemitted from living mice were acquired as photons/s/cm²/steridian (sr)using LIVINGIMAGE software (version 3.1) and integrated over 5 minutes.For photon quantification, a region of interest was manually selectedand kept constant for all experiments; the signal intensity wasconverted into photons/s/mm²/sr. For longitudinal comparison ofbioluminescence, baseline imaging was performed 24 h before kainic acidwas administered and bioluminescence was expressed as fold inductionover baseline levels for each mouse.

Primary neuron culture. Primary hippocampal neurons were isolated from16 days old CF1 embryos. Twenty-four-well culture plates were coatedwith 10 mg/ml Poly-L-Lysine (Sigma-Aldrich). Cells were seeded overnightat a density of 30,000 cells/well in DMEM/F-12 medium supplemented with10% FBS and penicillin/streptomycin, and subsequently maintained inNeurobasal medium containing 2% B27 supplement (Invitrogen). They wereaged for 6-7 days or 21-22 days, then challenged with 100 μM NMDA(N-Methyl-D-aspartic acid, Sigma-Aldrich) for 24 h in the presence andabsence of M-CSF or IL-34, and assayed for neurotoxicity or neuriticdystrophy, respectively. At the end of treatment, equal volume of 4% PFAwas added, plates incubated at room temperature for 15 min and thenwashed three times with PBS. Cells were kept in the last wash of PBS at4° C. till being counted or stained. For the neurotoxicity assay, liveand dead cells were counted according to their morphologies determinedby phase-contrast microscopy (Knowles et al., 2009; Yang et al., 2008).Results were expressed as % live cells. For quantification of neuriticdystrophy, the fixed cells were immunostained with a MAP-2 monoclonalantibody (1:5,000, Sigma-Aldrich). After overnight incubation, primaryantibody staining was revealed by an Alexa fluor 488-conjugatedsecondary antibody (Invitrogen). MAP2 positive dendrites were observedunder an invert fluorescence microscope (Olympus). Dendrites wereconsidered dystrophic when they showed a persistent pattern of increasedtortuosity (multiple abrupt turns). To quantify neurite curvature,neurite courses were digitized and approximated by a series of connectedline segments using ImageJ (NIH). The angle of each segment wasdetermined using a Sigmaplot macro, and the results were averaged togive the ‘mean differential curvature’ (Knowles et al., 2009; Yang etal., 2008). This parameter reflects the degree of neurite curvature withan increasing value indicating increased curvature. Neurite counting andquantification were performed in randomly selected fields (5fields/well) in a completely blinded manner.

B103 Neuroblastoma cells. B103 neuroblastoma cells were cultured inDulbecco's modified Eagle's medium containing 10% fetal calf serum and1% v/v penicillin/streptomycin (Invitrogen) in a 5% CO₂/95% airatmosphere. Ten thousand (10⁴) cells/well were seeded onto 24 wellplates (Corning Incorporated) and cultured for 24 h before NMDA wasadded. M-CSF or IL-34 was added 2 hrs before NMDA. Following a 24-hrincubation with NMDA, live and dead cells were assessed usingcalcein-acetoxymethyl ester (CAM) and SYTOX Orange (both fromInvitrogen, Carlsbad, Calif.), respectively. CAM is amembrane-permeable, fluorogenic esterase substrate that is hydrolyzedintracellularly to a green fluorescent product (calcein) in live cells.SYTOX Orange is a high-affinity nucleic acid stain that easilypenetrates cells with compromised plasma membranes and yet will notcross the membranes of live cells. After incubation with SYTOX Orange,the nucleic acids of dead cells fluoresce bright orange. The live anddead cells were observed under an invert fluorescence microscope(Olympus), where the live cells showed green color and the nuclei ofdead cells exhibited orange fluorescence. Five fields were randomlyselected from each well and the cell numbers were analyzed by ImageJ(NIH) in a blinded fashion. Cell survival was expressed as thepercentage of live cells over total number of the cells.

In situ hybridization. The cultured primary neurons (6-7 days inculture) were fixed with 4% paraformaldehyde. A 48-mer DNAoligonucleotide probe complementary to bases 904-951 of c-fms (Rothwelland Rohrschneider, 1987) was used for in situ hybridization. Theantisense oligonucleotide sequence is as follows:5′-GTTCATGGTGGCCGTGCGTGTGCCAACATCATTGCTGGCCACACAAGA-3′. The probe waslabeled at the 3′ end with digoxigenin (DIG). After fixation, the cellswere washed with PBS and exposed to proteinase K. Prehybridization wasperformed for 2 h at 42° C. with hybridization solution (Dako,Carpinteria, Calif.). Hybridization (probe concentration, 1 μg/ml) wascarried out in a humidified chamber at 42° C. overnight. Thehybridization signal was detected by a DIG Nucleic Acid Detection Kit orHNPP Fluorescent Detection Set (both from Roche Applied Science,Indianapolis, Ind.). The corresponding sense oligonucleotide probe wasused as a control.

M-CSF ELISA of human plasma. Human plasma samples were obtained fromacademic centers (Britschgi et al., 2009). Samples were diluted 1:10 andM-CSF was detected by Quantikine ELISA following the producer's manual(R&D Systems).

Data and statistical analysis. Data are presented as mean±SEM.Behavioral measurements were analyzed using Mann-Whitney rank sum testor 2-tailed Student's t test where appropriate. Bonferroni or Turkeypost-hoc test was used to compare pairs of groups following ANOVA.Statistical analysis was performed with Graphpad Prism software (version5). P<0.05 was considered statistically significant.

EXAMPLES

The following examples are put forth to provide those of ordinary skillin the art with a complete disclosure and description of how to make anduse the present invention; they are not intended to limit the scope ofwhat the inventors regard as their invention. Unless indicatedotherwise, part are parts by weight, molecular weight is averagemolecular weight, temperature is in degrees Centigrade, and pressure isat or near atmospheric.

Example 1 Systemic Administration of Macrophage-Colony StimulatingFactor (M-CSF) Improves Cognitive Function in hAPP-Transgenic Mice,Independent of Aβ Pathology

In earlier studies, the inventors of the present invention had observeda decreased concentration of macrophage-colony stimulating factor(M-CSF) in plasma from subjects suffering from Alzheimer's disease (‘ADplasma’) in comparison to plasma from healthy control subjects (‘controlplasma’). This observation, in combination with differentialconcentrations of other signaling proteins in AD plasma versus controlplasma can be used to diagnose Alzheimer's disease (Ray et al., 2007).In more recent studies, consistent with these findings, subjectssuffering from AD were found to exhibit significantly lower plasmalevels of M-CSF than age-matched, healthy control subjects (see FIG.1A), indicating a peripheral deficiency of M-CSF in subjects sufferingfrom AD.

To investigate in an animal model of Alzheimer's disease the effects ofelevated M-CSF concentrations, recombinant M-CSF was administeredsystemically to hAPP mice. In the hAPP mouse model of Alzheimer'sdisease mutant human amyloid precursor protein (hAPP) is expressed inneurons under control of the Thy1 promoter (Rockenstein et al., 2001).The hAPP mice, aka Thy1-hAPP transgenic mice, model early Alzheimer'sdisease-like brain pathology and cognitive impairments. Recombinanthuman M-CSF or PBS as control was injected intraperitoneally three timesa week for 10 weeks into both 6-month-old hAPP mice and their wildtypelittermates at a dose of 800 μg/kg body weight; this dosage had beenused clinically in human bone marrow transplantation patients(Nemunaitis et al., 1993). After 10 weeks of treatment, all mice wereassessed for learning and memory function using the Morris water maze(MWM), a test of spatial learning for rodents that relies on distal cuesto navigate from start locations around the perimeter of an openswimming arena to locate a submerged escape platform, and probe trialsto assess reference memory (Morris, 1981; Vorhees & Williams, 2006).M-CSF-treated hAPP mice showed significantly better behavioral outcomesthan PBS-injected hAPP mice, as indicated by shorter escape latencies inthe hidden platform tests (see FIG. 1B).

In further experiments, recombinant human M-CSF or PBS as control (i.p.,800 μg/kg body weight) was injected three times a week into18-20-month-old hAPP and wildtype mice for only 4 weeks to determinewhether M-CSF administration could improve memory function in olderanimals which already exhibited behavioral deficits (see FIG. 1C/D), andwhether a shorter period of treatment would exert similarly beneficialeffects. M-CSF treatment significantly reduced memory deficits in hAPPmice in both the Morris Water Maze (see FIG. 1 E) and in the probe trial(see FIG. 1F). Thus, M-CSF treatment had ameliorated learning and memorydeficits in hAPP mice in all tested modalities.

To determine whether M-CSF exerted the described beneficial effects byaltering Aβ accumulation or aggregation in the brain, both soluble andinsoluble levels of Aβ1-x and Aβ1-42 were measured by ELISA immunoassay.No significant changes were observed in the hippocampus or cortex ofhAPP mice following M-CSF treatment (Table 1). Similarly, no differencewas found in anti-human Aβ1-5 (3D6 antibody) immunoreactivity (see FIG.2A-C) or the number of plaques in M-CSF compared with PBS injectedanimals (see FIG. 2D). Therefore, the beneficial effects of M-CSF oncognitive function are likely independent of Aβ accumulation. Moreover,no effects of M-CSF were observed on activation of microglia assessed asa function of CD68 expression by immunoreactivity (Luo et al., 2006);immunoreactivity assessed by percentage of occupied area was1.152±0.354% in M-CSF-treated hAPP mice vs 0.721±0.169% in PBS-injectedgroup, P=0.289 by t test.

TABLE 1 Effect of M-CSF treatment on cerebral Aβ levels in hAPP mice.M-CSF treatment did not affect cerebral Aβ levels. hAPP mice and theirwildtype (WT) littermates (n = 9-10 mice per genotype, 5.5-6.5 months ofage) were injected with M-CSF or PBS (i.p., 800 μg/kg) three times aweek for 10 weeks. Mice were sacrificed, and hippocampus and cortex weredissected from one hemibrain. Sequential extractions using RIPA and 70%Formic Acid (FA) buffers were performed on the hemibrains and Aβ wasmeasured by ELISA to detect human Aβ1-x, and Aβ1-42. No significantdifferences were observed between M-CSF or PBS treated groups. BrainRegion Extraction Groups Aβ_(1-x) (ng/g) Aβ₁₋₄₂ (ng/g) Neocortex RIPAhAPP/PBS 13.210 ± 3.070 1.324 ± 0.097 hAPP/M-CSF 15.020 ± 2.895 1.422 ±0.214 FA hAPP/PBS  9635.0 ± 1863.0 1220.0 ± 245.1  hAPP/M-CSF 11568.0 ±2493.0 1605.0 ± 413.9  Hippocampus RIPA hAPP/PBS  1.018 ± 0.268 0.563 ±0.091 hAPP/M-CSF  1.246 ± 0.198 0.731 ± 0.177 FA hAPP/PBS 3539.0 ± 991.7725.5 ± 247.4 hAPP/M-CSF  6879.0 ± 2045.0 [00109] ± 302.9   Values aremean ± SEM; n = 10 for hAPP/PBS, 9 for hAPP/M-CSF.

Example 2 Systemic Administration of M-CSF Reduces Kainic Acid-InducedNeurodegeneration

To explore whether systemically administered M-CSF exerts protectiveeffects on neurons, M-CSF was administered systemically in a mouse modelof kainic acid-induced neurodegeneration. Subcutaneous administration ofkainic acid (20 mg/kg) into wildtype FVB/N mice resulted in severeseizures (highest seizure score 6.4±1.3), with significant degenerationof neurons in the pyramidal layer (FIG. 3A) and reduced hippocampalcalbindin immunoreactivity (FIG. 3C) upon postmortem pathologicalexamination, consistent with previous reports (Luo et al., 2006). Incontrast, wildtype FVB mice injected intraperitoneally with recombinant,human M-CSF (800 μg/kg body weight) 24 h prior to kainic acidadministration showed little hippocampal cell loss (see FIG. 3A/B) andcalbindin reduction (see FIG. 3C/D), although they suffered from similarseizure activity (highest seizure score 6.2±1.7). In line with thesefindings, systemic M-CSF administration significantly reduced theincrease in levels of Neuropeptide Y (NPY) in the hippocampus associatedwith kainic acid lesioning (FIG. 3E/F). Thus, systemic administration ofM-CSF attenuated kainic acid-induced excitotoxic neurodegeneration andprovided significant neuroprotection in vivo in FVB mice.

Example 3 M-CSF Inhibits Kainic Acid-Induced Microgliosis

Glial cells are non-neuronal cells that surround and insulate neuronsfrom one another, supply oxygen and nutrients to neurons, destroypathogens and remove dead neurons.

Microglia are the smallest of the glial cells and are generallyconsidered the resident macrophages of the brain and the spinal cord,acting as the first form of active immune defense in the central nervoussystem. Microglial cells can become activated by a single stimulus suchas neuron damage, lipopolysaccharide or kainic acid administration, andin response release neurotoxic factors, including tumor necrosisfactor-a, nitric oxide, interleukin-1β, and reactive oxygen species thatall drive progressive neuron damage (Lull & Block, 2010); this is knownas reactive microgliosis.

Glial cells are sensitive to neuronal dysfunction and damage, andmarkers associated with activation of microglia are frequently used asindicators of neuronal injury and neurodegeneration (Luo et al., 2006).To investigate whether M-CSF inhibits inflammatory processes, theactivation of microglia was analyzed as a function of CD68immunoreactivity (Luo et al., 2006).

Kainic acid injection into two-months-old FVB/N mice caused massiveactivation of microglia in the hippocampus (see FIG. 3G/H), which wasalmost completely prevented by intraperitoneal application ofrecombinant human M-CSF (see FIG. 3G/H). When microglial activation wasquantified with an antibody against the activation marker, CD11b,immunoreactivity, as assessed by percentage of occupied area, was3.948±0.1997% in the kainic acid/M-CSF-pretreated group versus4.664±0.04571% in the kainic acid/PBS group (control group), P=0.001 byt test).

In contrast, no difference was found in immunoreactivity for Iba-1, amicroglial marker that does not change much in response to activation(immunoreactivity assessed by percentage of occupied area was0.345±0.009% in the kainic acid/M-CSF-pretreated group versus0.368±0.007% in the kainic acid/PBS group (control group), P=0.569 by ttest), suggesting that the number of microglia was not significantlyaltered by administration of recombinant human M-CSF.

To investigate whether activated microglia originated from localresident cells or from the periphery and whether the administration ofrecombinant human M-CSF caused infiltration of peripheral (myeloid)cells into the brain, mice were parabiosed in which two mice share acommon blood supply after being joined surgically at their flanks(Conboy et al., 2005). Actin-green fluorescent protein (Actin-GFP)transgenic mice (Okabe et al., 1997) were paired with wildtype mice (seeFIG. 4) and wildtype parabionts were analyzed for GFP+ cells in thebrain 6 weeks later. In the control parabionts, there were few GFP+cells in the brain (see FIG. 4B), consistent with previous studies(Ajami et al., 2007), and treatment with recombinant human M-CSF did notsignificantly increase the number of GFP+ cells. Likewise, nosignificant difference was detected in the numbers of GFP+ cells inkainic acid-injected mice, with or without prior M-CSF treatment (seeFIG. 4B). In addition, similar results were obtained from hAPPparabionts (see FIG. 4B). These data suggest that M-CSF does not exertits neuroprotective effects by recruiting peripheral myeloid or othercells to the brain in response to excitotoxicity or in the hAPP mousemodel.

Example 4 The M-CSF Receptor, C-FMS, is Expressed in Neurons andUpregulated Following Neuronal Injury

To determine the potential target cell of M-CSF responsible for thebeneficial effects in the excitotoxicity model we studied the expressionof its receptor, c-Fms, in the brain. We first tested 6 differentcommercially available c-Fms antibodies, some of which had been used inthe literature to stain brain tissues in the past, but found that noneof them produced specific staining that was absent in c-Fms knockoutmice (Li et al., 2006). We therefore employed a transgenic reportermouse, which expresses EGFP under control of the c-fms promoter (Burnettet al., 2004). The expression of EGFP was detected with immunostainingusing an anti-GFP antibody, which produced no immunostaining in brainsof wildtype mice (FIG. 5). We observed a broad, predominantly microglialexpression pattern of the reporter gene throughout the normal, uninjuredmouse brain (FIGS. 6A and 5B-5E), consistent with reports in theliterature (Raivich et al., 1998; Sherr et al., 1985). Weaker butdiscernable reporter immunoreactivity was also seen in few, scatteredneurons (1.639±0.217%) throughout the brain. In the hippocampus, theseneurons were observed in the CA2/3 regions and in the dentate gyrus(FIGS. 6C and 5B-5E). To confirm these findings and validate thereporter mice, we cultured primary hippocampal neurons isolated fromthese mice and analyzed the expression of c-fms mRNA by in situhybridization. Seven-day-old primary neurons clearly expressed c-fmsmRNA, which was co-localized with EGFP (FIGS. 6E and 7). The expressionof c-Fms in neurons was further confirmed in separate lineage tracingstudies using a cross between c-fms-iCre and Rosa-flox-stop-CFP mice(FIG. 8). In double transgenic reporter mice, cre recombinase expressionin cells with an active c-fms promotor results in deletion of atranscriptional stop sequence and consequent expression of CFP. Again,small numbers of neurons (1.8% in the cortex) throughout the brainshowed clear reporter gene expression (FIG. 7).

To determine if c-Fms expression is increased after injury we lesionedmice with kainic acid and found that systemic or intracerebroventricularadministration of the toxin, leads to prominent up-regulation of thec-Fms reporter (FIGS. 6B/D, 5B/E, 9). At 6 h after kainic acidadministration, reporter expression was increased not only in microgliabut clearly also in neurons (36.52±7.125%) (FIGS. 6/D, 5B-E, 9).Reporter expression continued to increase in microglia at 24 h (FIGS.5B-E) and up until 5 days but decreased again in neurons (data notshown). These results demonstrate that the c-Fms gene is expressed inneurons and upregulated after excitotoxic injury.

Example 5 Depleting M-CSF Receptor (M-CSFR) in Neurons IncreasesSusceptibility to Excitotoxic Injury

To study the potential significance of neuronal M-CSF signaling wedeleted the receptor specifically in forebrain neurons. We generatedc-Fms-null mutant mice (c-fms^(f/f)-cre) by breeding mice with aloxP-c-fms-loxP insertion (Li et al., 2006) (c-fms^(f/f)) withCaMKIIα-cre transgenic mice (Fan et al., 2001). We comparedc-fms^(f/f)-cre mice and their wildtype littermates after stereotaxicinjection of PBS into the right and kainic acid (50 ng) into the leftdorsal hippocampus (FIG. 10). In spite of similar seizure severitybetween c-fms^(f/f)-cre and wildtype mice (highest seizure score was4.6±1.5 in wildtype vs 4.9±1.7 in mutant mice), mutant mice died attwice the rate of wildtypes (mortality was 16% in wildtype vs 30% inmutant, P=0.042). Moreover, surviving c-fms^(f/f)-cre mice showedsignificantly more neurodegeneration and neuroinflammation than wildtypelittermates (FIG. 11). While cell loss was restricted to the pyramidalcell layer of the CA3 region in wildtype littermates (FIG. 11A), it wasmore profound and widespread, spanning the whole CA3 and CA1 regions inc-fms^(f/f)-cre mice (FIG. 11A/B).

Similarly, calbindin immunoreactivity was depleted more severely in theCA1 subfield in kainic acid injected c-fms^(f/f)-cre compared withwildtype littermates (FIG. 11C/D). This increase in susceptibility toexcitotoxic neurodegeneration in c-fms^(f/f)-cre mice was mirrored by anincrease in the microglial response. Microglial activation measured byCD68 expression was markedly increased in c-fms^(f/f)-cre compared withwildtype mice (FIG. 11E/F). In wildtype mice, microgliosis was observedonly on the ipsilateral side, whereas in c-fms^(f/f)-cre mice, it wasalso observed on the contralateral hippocampus (FIG. 11E). In summary,mice lacking c-Fms in neurons were more susceptible to death andneurodegeneration following excitotoxic injury, supporting a directprotective and survival function of endogenous M-CSF signaling inneurons.

Example 6 Endogenous M-CSF is Upregulated in Neurons Following NeuronalInjury

In the uninjured brain, faint M-CSF immunostaining was observablethroughout the brain, which was absent in M-CSF deficient op/op mice(FIG. 12), thus confirming specificity of the antibody. In contrast,kainic acid administration led to a progressive increase of M-CSFimmunoreactivity in the hippocampus, first in CA3 at 6 h, and thenthroughout the hippocampus at 24 h (FIG. 13). M-CSF immunoreactivity waslocalized mostly to neurons (FIG. 13). While M-CSF expression variedsignificantly among individual animals immunoreactivity showed aremarkable inverse correlation with neuronal cell loss at day 3(R=−0.731, P=0.023) (FIG. 13). In agreement with this inversecorrelation between M-CSF expression and neurodegeneration we found astriking lack of M-CSF immunoreactivity in mice, which had died within 6h after kainic acid administration (n=6 mice, FIG. 13A). Together, theseresults are consistent with the possibility that upregulation of localM-CSF in the brain serves to protect neurons from degeneration and celldeath.

Example 7 M-CSF Activates Neuronal CREB Pathway

Further studies were directed to investigate whether M-CSF might actdirectly on neurons, thereby activating c-Fms coupled intracellularpathways. Of these, cAMP responsive element binding protein (CREB)signaling appears to play a major role in mediating M-CSF's biologicaleffects in macrophages (Casals-Casas et al., 2009). Importantly, kainicacid injury was shown to selectively decrease phosphorylation of CREB(p-CREB) in vulnerable regions but the cause for this decrease was notidentified (Ferrer et al., 2002). Since CREB has a key function inneuronal survival (Walton and Dragunow, 2000) we reasoned that M-CSFmight activate CREB in neurons as well. Indeed, at 6 h after kainic acidadministration, p-CREB immunoreactivity was reduced in CA3 neurons,notably without obvious cell loss at this early time point (FIG. 14A/B).Systemic treatment with M-CSF significantly increased p-CREBimmunoreactivity (FIG. 14A/B), and p-CREB protein as measured by Westernblot from hippocampal lysates (FIG. 14C/D). These results show thatM-CSF can activate CREB in neurons. To confirm the role of CREB in M-CSFmediated neuronal survival, we infused the CREB signaling inhibitorKG501, or PBS as control into the right dorsal hippocampus of wildtypeFVB/N mice using osmotic minipumps. KG501 is a small molecule compoundthat interrupts the interaction between p-CREB and CBP (CREB bindingprotein) (Best et al., 2004). Kainic acid was subcutaneouslyadministered 2 days after infusion of KG501. Kainate-induced excitotoxicinjury was significantly reduced by systemic treatment with M-CSF inPBS-infused controls, but not in KG501-infused animals (FIG. 14E/F).These results show that blocking CREB signaling interferes with thetrophic and survival effects of M-CSF and suggests that CREB mediates atleast part of the beneficial effects of M-CSF, supporting a direct roleof M-CSF in neuronal function.

Example 8 MCSF and IL-34 Protect Neuroblastoma B103 Cells and PrimaryNeurons Against Excitotoxic Injury and Activate the CREB Pathway

To test the possibility that M-CSF acts through neurons, we investigatedwhether M-CSF possesses the capacity to directly protect neurons fromexcitotoxicity in cell culture, in the absence of microglia. Indeed,while exposure of B103 neuroblastoma cells to NMDA caused substantialcell death M-CSF significantly reduced cell death (FIGS. 15A/B, 16).Likewise, the newly identified c-Fms ligand IL-34 showed similarprotection against NMDA (FIGS. 15B, 16). In line with these findings,incubation with M-CSF or IL-34 significantly increased p-CREB asmeasured by Western blotting from cell lysates (FIG. 15C). Treatment ofcells with GW2580 (Conway et al., 2005), a c-Fms kinase inhibitor,completely blocked M-CSF or IL-34 mediated protection (FIG. 15B). Inaddition, the CREB inhibitor KG501 also blocked M-CSF or IL-34 mediatedprotection (FIG. 15B). These results demonstrate that M-CSF, as well asIL-34 can activate CREB signaling via c-Fms receptors and increasesurvival of neuroblastoma cells injured with excitotoxins.

Similarly, NMDA induced cell death was significantly reduced by M-CSF orIL-34 in primary neurons (FIG. 15D). Moreover, exposure of hippocampalprimary neurons to NMDA caused neuritic dystrophy, characterized by thepresence of varicosities and excessive tortuosity (FIGS. 15E, 17). Thesedystrophic changes were prevented almost completely by M-CSF and IL-34(FIG. 15E, 17). Assessment of dystrophy by visual criteria (FIG. 17E)and by quantification of the neurite mean differential curvature, ameasure of tortuosity, showed that M-CSF and IL-34 effectively blockedNMDA-induced dystrophy (FIG. 15F). Taken together, these results showthat c-FMS ligands protect cultured neurons against NMDA excitotoxicinjury, in part through activation of CREB signaling.

Example 9 Strong Neuroprotective Effects of Systemically AdministeredIL-34

To determine whether IL-34 provides neuroprotection against excitotoxicinjury in vivo we administered recombinant IL-34 (100 μg/kg)systemically in FVB/N mice lesioned by kainate. Mice receiving IL-34showed significantly reduced neuronal cell loss and calbindin reductionin the pyramidal cell layer of the hippocampus (FIG. 18). These resultsdemonstrate that systemic administration of recombinant IL-34 attenuatesexcitotoxic injury and provides similar neuroprotection as recombinantM-CSF.

Example 10 Strong Neuroprotective Effects of Recombinant Human M-CSFAdministered Post Neuronal Injury

Further studies investigated the clinical potential of M-CSF toattenuate neurodegeneration after an injurious insult had occurred. Inorder to follow injury and neurodegeneration in individual mice overtime we used bioluminescent reporter mice expressing luciferase underthe control of a GFAP promoter (Luo et al., 2007; Zhu et al., 2004) andadministered M-CSF at different time points before or after kainic acidinduced injury. Neuronal injury is closely tied to activation ofastrocytes and kainic acid-induced bioluminescence in GFAP-luc micecorrelates significantly with hippocampal cell death (Zhu et al., 2004).Accordingly, kainic acid injection led to a reproducible, significantincrease in bioluminescence in the brain, peaking at 24 h and slowlydecreasing until day 5 (FIG. 19A/B). Notably, systemic M-CSFpretreatment (800 μg/kg body weight) at 24 h or 2 h before kainic acidadministration significantly inhibited astrogliosis at day 3 and 5,consistent with reduced neuroinflammation and neuronal damage (FIGS. 3and 19B). Surprisingly, mice receiving M-CSF (800 μg/kg body weight) at2 or 6 h after kainic acid showed similar and significant reduction ofastrogliosis (FIG. 19C). Attenuated neurodegeneration in these mice wasconfirmed by pathological analysis (FIGS. 19D-G). Thus, these resultsdemonstrate that M-CSF is sufficient to promote neuronal survival andreduce glial activation.

Although the foregoing invention and its embodiments have been describedin some detail by way of illustration and example for purposes ofclarity of understanding, it is readily apparent to those of ordinaryskill in the art in light of the teachings of this invention thatcertain changes and modifications may be made thereto without departingfrom the spirit or scope of the appended claims. Accordingly, thepreceding merely illustrates the principles of the invention. It will beappreciated that those skilled in the art will be able to devise variousarrangements which, although not explicitly described or shown herein,embody the principles of the invention and are included within itsspirit and scope.

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What is claimed is:
 1. A method of attenuating neuronal damage in ahuman subject following acute central nervous system injury, the methodcomprising administering a pharmaceutical composition comprising atleast one macrophage colony stimulating factor receptor agonist to saidhuman within a predetermined time period following said acute centralnervous system injury, wherein said macrophage colony stimulating factorreceptor agonist is Interleukin-34 (IL-34) or a biologically activefragment thereof.
 2. The method of claim 1, wherein said acute centralnervous system injury is caused by a traumatic brain injury, cerebralischemia, cerebral glucose deprivation, cerebral oxidative stress,spinal cord injury or excitotoxic injury.
 3. The method of claim 1,wherein the agonist comprises IL-34.
 4. The method of claim 1, whereinthe agonist comprises a biologically active fragment of IL-34.
 5. Amethod of stimulating neuronal repair in a human subject following acutecentral nervous system injury, the method comprising administering apharmaceutical composition comprising at least one macrophage colonystimulating factor receptor agonist to said human within a predeterminedtime period following said acute central nervous system injury, whereinsaid macrophage colony stimulating factor receptor agonist isInterleukin-34 (IL-34) or a biologically active fragment thereof.
 6. Themethod of claim 5, wherein said acute central nervous system injury iscaused by a traumatic brain injury, cerebral ischemia, cerebral glucosedeprivation, cerebral oxidative stress, spinal cord injury orexcitotoxic injury.
 7. The method of claim 5, wherein the agonistcomprises IL-34.
 8. The method of claim 5, wherein the agonist comprisesa biologically active fragment of IL-34.
 9. A method of stimulatingneuronal repair in a human subject suffering from Alzheimer's disease,the method comprising administering a pharmaceutical compositioncomprising at least one macrophage colony stimulating factor receptoragonist to said human during the course of said Alzheimer's disease,wherein said macrophage colony stimulating factor receptor agonist isInterleukin-34 (IL-34) or a biologically active fragment thereof. 10.The method of claim 9, wherein the agonist comprises IL-34.
 11. Themethod of claim 9, wherein the agonist comprises a biologically activefragment of IL
 34. 12. A method of attenuating neuronal damage in ahuman subject at risk of Alzheimer's disease, the method comprisingadministering a pharmaceutical composition comprising at least onemacrophage colony stimulating factor receptor agonist to said humansubject prior to onset of Alzheimer's disease, wherein said macrophagecolony stimulating factor receptor agonist is Interleukin-34 (IL-34) ora biologically active fragment thereof.
 13. The method of claim 12,wherein the agonist comprises IL-34.
 14. The method of claim 12, whereinthe agonist comprises a biologically active fragment of IL-34.
 15. Amethod of attenuating neuronal damage in a human subject suffering fromAlzheimer's disease, the method comprising administering apharmaceutical composition comprising at least one macrophage colonystimulating factor receptor agonist to said human subject during thecourse of said Alzheimer's disease, wherein said macrophage colonystimulating factor receptor agonist is Interleukin-34 (IL-34) or abiologically active fragment thereof.